..."While his wife was away on business he killed his eldest daughter and, because his son saw what he had done, he killed his son as well. When the wife came home, he offered her food, saying: 'We have meat.'...

Well cannibalism become fairly widespread during the '95 - 98' famine in the north. That comes directly from defectors who survived that period. The economic situation there has barely improved much during the intervening period, so it should hardly come as a surprise that it may be happening (or is continuing to happen) again.

Do I believe the article? Not necessarily. How in the world would this story get out??

Rather easily with Chinese cell phones. Several NGOs working on North Korean issues have sources that live on the North Korean side of the Chinese border. Take a look at some of the media sources specifically dedicated to North Korea. They report all the time from their sources.